SMC gene family

Genes in the structural maintenance of chromosomes (SMC) family provide instructions for making proteins that help regulate the structure and organization of chromosomes. Researchers have identified at least six SMC proteins, SMC1 through SMC6. (SMC1 usually refers to the protein made from either the SMC1A or the SMC1B gene.) SMC proteins have diverse functions within cells. In addition to organizing chromosomes, they are also involved in regulating the activity of genes, stabilizing cells' genetic information, and repairing damaged DNA.

SMC proteins interact with one another in pairs to form the core of several protein complexes. The most important of these complexes are cohesin and condensin.

Cohesin is made up of the SMC1 and SMC3 proteins, as well as two regulatory proteins. This protein complex helps control the activity of chromosomes during cell division. Before cells divide, they must copy all of their chromosomes. The copied DNA from each chromosome is arranged into two identical structures, called sister chromatids, which are attached to one another during the early stages of cell division. Cohesin holds the sister chromatids together.

Condensin is made up of the SMC2 and SMC4 proteins, along with three regulatory proteins. This protein complex helps determine the shape and structure of chromosomes during cell division. Within the nucleus, chromosomes are usually present as loose, tangled strands of DNA. However, when cells prepare to divide, the chromosomes are packed, or condensed, into tightly coiled structures. Condensin attaches to DNA to form these compacted chromosomes prior to cell division.

The SMC5 and SMC6 proteins also interact with one another, although less is known about their function. Studies suggest that they may form a protein complex that is involved in DNA repair.